I've seen the 'bad blood' issue happen at a place I formerly worked at, that I refer to as 'MegaBank' (which isn't short of the truth). One was developer that seemingly left on good terms, but sneakily deleted a load of prod data as he was 'clearing down his inbox', and another that smashed up an office. Which was why, after the latter, the 'reduction in force' meetings were conducted on a separate floor with security guards.